1. The Reproductive System: Part C27
The Reproductive System: Part C

2. Establishing the Ovarian Cycle
During childhood, until puberty
Ovaries secrete small amounts of estrogens
Estrogen inhibits release of GnRH

3. Establishing the Ovarian Cycle
At puberty
Leptin from adipose tissue decreases the estrogen inhibition
GnRH, FSH, and LH are released
In about four years, an adult cyclic pattern is achieved and menarche occurs

4. Hormonal Interactions During a 28-Day Ovarian Cycle
Day 1: GnRH  release of FSH and LH
FSH and LH  growth of several follicles, and estrogen release
 estrogen levels
Inhibit the release of FSH and LH
Stimulate synthesis and storage of FSH and LH
Enhance further estrogen output

5. Hormonal Interactions During a 28-Day Ovarian Cycle
Estrogen output by the vesicular follicle increases
High estrogen levels have a positive feedback effect on the pituitary at midcycle
Sudden LH surge at day 14

6. Hormonal Interactions During a 28-Day Ovarian Cycle
Effects of LH surge
Completion of meiosis I (secondary oocyte continues on to metaphase II)
Triggers ovulation
Transforms ruptured follicle into corpus luteum

7. Hormonal Interactions During a 28-Day Ovarian Cycle
Functions of corpus luteum
Produces inhibin, progesterone, and estrogen
These hormones inhibit FSH and LH release
Declining LH and FSH ends luteal activity and inhibits follicle development

8. Hormonal Interactions During a 28-Day Ovarian Cycle
Days 26–28: corpus luteum degenerates and ovarian hormone levels drop sharply
Ends the blockade of FSH and LH
The cycle starts anew

9. Early and midfollicular phases
Hypothalamus
Hypothalamus 5
GnRH
Positive
feedback exerted
by large in
estrogen
output. 4 8
Travels via
portal blood 1
Anterior pituitary 1 5
Progesterone
Estrogen
Inhibin
LH surge
FSH LH
Ruptured
follicle 6 2 2 8
Slightly
elevated
estrogen
and rising
inhibin
levels. 3 7
Thecal
cells
Granulosa
cells
Androgens
Corpus luteum
Mature follicle
Ovulated
secondary
oocyte
Convert
androgens to
estrogens
Inhibin 2
Late follicular and
luteal phases
Early and midfollicular phases
Figure 27.19

10. (a) Fluctuation of gonadotropin levels: FluctuatingLH
FSH
(a) Fluctuation of gonadotropin levels: Fluctuating
levels of pituitary gonadotropins (follicle-stimulating
hormone and luteinizing hormone) in the blood
regulate the events of the ovarian cycle.
Figure 27.20a

11. (b) Ovarian cycle: Structural changes in the ovarian
Primary
follicle
Vesicular
follicle
Corpus
luteum
Degenerating
corpus luteum
Secondary
follicle
Ovulation
Follicular
phase
Ovulation
(Day 14)
Luteal
phase
(b) Ovarian cycle: Structural changes in the ovarian
follicles during the ovarian cycle are correlated with
(d) changes in the endometrium of the uterus during
the uterine cycle.
Figure 27.20b

12. Uterine (Menstrual) Cycle
Cyclic changes in endometrium in response to ovarian hormones
Three phases
Days 1–5: menstrual phase
Days 6–14: proliferative (preovulatory) phase
Days 15–28: secretory (postovulatory) phase (constant 14-day length)

13. Uterine Cycle Menstrual phase
Ovarian hormones are at their lowest levels
Gonadotropins are beginning to rise
Stratum functionalis is shed and the menstrual flow occurs

14. Uterine Cycle Proliferative phase
Estrogen levels prompt generation of new functional layer and increased synthesis of progesterone receptors in endometrium
Glands enlarge and spiral arteries increase in number

15. Uterine Cycle Secretory phase Progesterone levels prompt
Further development of endometrium
Glandular secretion of glycogen
Formation of the cervical mucus plug

16. (c) Fluctuation of ovarian hormone levels:
Estrogens
Progesterone
(c) Fluctuation of ovarian hormone levels:
Fluctuating levels of ovarian hormones (estrogens
and progesterone) cause the endometrial changes
of the uterine cycle. The high estrogen levels are
also responsible for the LH/FSH surge in (a).
Figure 27.20c

17. (d) The three phases of the uterine cycle:
Endometrial
glands
Blood vessels
Menstrual
flow
Functional layer
Basal layer
Days
Menstrual
phase
Proliferative
phase
Secretory
phase
(d) The three phases of the uterine cycle:
• Menstrual: Shedding of the functional layer of the
endometrium.
• Proliferative: Rebuilding of the functional layer of
the endometrium.
• Secretory: Begins immediately after ovulation.
Enrichment of the blood supply and glandular secretion of
nutrients prepare the endometrium to receive an embryo.
Both the menstrual and proliferative phases occur before ovulation, and
together they correspond to the follicular phase of the ovarian cycle. The
secretory phase corresponds in time to the luteal phase of the ovarian cycle.
Figure 27.20d

18. If fertilization does not occur
Uterine Cycle
If fertilization does not occur
Corpus luteum degenerates
Progesterone levels fall
Spiral arteries kink and spasm
Endometrial cells begin to die
Spiral arteries constrict again, then relax and open wide
Rush of blood fragments weakened capillary beds and the functional layer sloughs

19. Effects of Estrogens
Promote oogenesis and follicle growth in the ovary
Exert anabolic effects on the female reproductive tract
Support the rapid but short-lived growth spurt at puberty

20. Induce secondary sex characteristics
Effects of Estrogens
Induce secondary sex characteristics
Growth of the breasts
Increased deposit of subcutaneous fat (hips and breasts)
Widening and lightening of the pelvis

21. Effects of Estrogens Metabolic effects
Maintain low total blood cholesterol and high HDL levels
Facilitates calcium uptake

22. Effects of Progesterone
Progesterone works with estrogen to establish and regulate the uterine cycle
Effects of placental progesterone during pregnancy
Inhibits uterine motility
Helps prepare the breasts for lactation

23. Female Sexual Response
Initiated by touch and psychological stimuli
The clitoris, vaginal mucosa, and breasts engorge with blood
Vestibular gland secretions lubricate the vestibule
Orgasm is accompanied by muscle tension, increase in pulse rate and blood pressure, and rhythmic contractions of the uterus

24. Female Sexual Response
Females do not have a refractory period after orgasm and can experience multiple orgasms in a single sexual experience
Orgasm is not essential for conception

25. Sexually Transmitted Infections (STIs)
Also called sexually transmitted diseases (STDs) or venereal diseases (VDs)
The single most important cause of reproductive disorders

26. Gonorrhea
Bacterial infection of mucosae of reproductive and urinary tracts
Spread by contact with genital, anal, and pharyngeal mucosae

27. Gonorrhea Signs and symptoms
Males
Urethritis, painful urination, discharge of pus
Females
20% display no signs or symptoms
Abdominal discomfort, vaginal discharge, or abnormal uterine bleeding
Can result in pelvic inflammatory disease and sterility
Treatment: antibiotics, but resistant strains are becoming prevalent

28. Bacterial infection transmitted sexually or contracted congenitally
Syphilis
Bacterial infection transmitted sexually or contracted congenitally
Infected fetuses are stillborn or die shortly after birth
Infection is asymptomatic for 2–3 weeks
A painless chancre appears at the site of infection and disappears in a few weeks

29. Syphilis
If untreated, secondary signs appear several weeks later for 3–12 weeks, and then disappear: pink skin rash, fever, and joint pain
The latent period may or may not progress to tertiary syphilis, characterized by gummas (lesions of the CNS, blood vessels, bones, and skin)
Treatment: penicillin

30. Chlamydia Most common bacterial STI in the United States
Responsible for 25–50% of all diagnosed cases of pelvic inflammatory disease
Symptoms: urethritis; penile and vaginal discharges; abdominal, rectal, or testicular pain; painful intercourse; irregular menses
Can cause arthritis and urinary tract infections in men, and sterility in women
Treatment: tetracycline

31. Viral Infections Genital warts Caused by human papillomavirus (HPV)
Second most common STI in the United States
Increase the risk of cancers in infected body regions

32. Caused by human herpes virus type 2
Viral Infections
Genital herpes
Caused by human herpes virus type 2
Characterized by latent periods and flare-ups
Congenital herpes can cause malformations of a fetus
Treatment: acyclovir and other antiviral drugs

33. Developmental Aspects: Determination of Genetic Sex
One of the 23 pairs of chromosomes in body cells are sex chromosomes: X and Y
Females are XX and each egg has an X chromosome
Males are XY, so ~50% of sperm contain X, ~50% contain Y

34. Developmental Aspects: Determination of Genetic Sex
X egg + X sperm  XX (female offspring)
X egg + Y sperm  XY (male offspring)
The SRY gene on the Y chromosome initiates testes development and maleness

35. Developmental Aspects: Sexual Differentiation
Sexually indifferent stage
Gonads begin development in fifth week as gonadal ridges
Paramesonephric (Müllerian) ducts (future female ducts) form lateral to the mesonephric (Wolffian) ducts (future male ducts)
Primordial germ cells migrate to the gonadal ridges to provide germ cells destined to become spermatogonia or oogonia
Gonads begin development in seventh week in males, eighth week in females

36. sexually indifferent stage
Mesonephros
Mesonephric
(Wolffian) duct
Gonadal ridge
Paramesonephric
(Müllerian) duct
Metanephros
(kidney)
Cloaca
5- to 6-week embryo:
sexually indifferent stage
Figure (1 of 5)

37. Testes Efferent ductules Epididymis Paramesonephric
duct (degenerating)
Mesonephric duct
forming the ductus
deferens
Urinary bladder
Seminal vesicle
Urogenital sinus
forming the urethra
7- to 8-week male embryo
Figure (2 of 5)

38. Ovaries Paramesonephric duct forming the uterine tube Mesonephric duct
(degenerating)
Fused
paramesonephric
ducts forming
the uterus
Urinary bladder
(moved aside)
Urogenital sinus
forming the urethra
and lower vagina
8- to 9-week female fetus
Figure (3 of 5)

39. Developmental Aspects: Development of External Genitalia
Genital tubercle  penis of male; clitoris of female
Urethral fold  urethra of male; labia minora of female
Labioscrotal folds  scrotum of male: labia majora of female

40. Genital tubercle Urethral fold Labioscrotal Anus swelling Tail (cut)
Urethral groove
(a) Indifferent
Figure 27.22a

41. Approximately 5 weeks Glans penis Labioscrotal Urethral swellings
(scrotum)
Urethral
folds
Anus
Glans penis
Penis
Scrotum
Anus
(b) Male development
Figure 27.22b

42. Genital tubercle Urethral fold Labioscrotal Anus swelling Tail (cut)
Urethral groove
(a) Indifferent
Figure 27.22a

43. (c) Female development
Approximately 5 weeks
Glans clitoris
Urogenital
sinus
Labioscrotal
swellings
(labia majora)
Urethral
folds
(labia
minora)
Anus
Glans clitoris
Labia majora
Labia
minora
Anus
(c) Female development
Figure 27.22c

44. Development Aspects: Descent of the Gonads
About two months before birth
Testosterone stimulates the migration of the testes toward the scrotum
Ovaries also descend, but are stopped by the broad ligament at the pelvic brim
Gubernaculum: fibrous cord from each testis to the scrotum or from ovary to labium majus; guides the descent

45. At birth: male development
Urinary bladder
Seminal vesicle
Prostate
Bulbourethral gland
Ductus deferens
Urethra
Efferent ductules
Epididymis
Testis
Penis
At birth: male development
Figure (4 of 5)

46. At birth: Female development
Uterine tube
Ovary
Uterus
Urinary bladder
(moved aside)
Vagina
Urethra
Hymen
Vestibule
At birth: Female development
Figure (5 of 5)

47. Development Aspects: Puberty
In response to rising levels of gonadal hormones
Reproductive organs grow to adult size and become functional
Secondary sex characteristics appear
Earliest time that reproduction is possible

48. Menopause
Has occurred when menses have ceased for an entire year
There is no equivalent to menopause in males

49. Declining estrogen levels 
Menopause
Declining estrogen levels 
Atrophy of reproductive organs and breasts
Irritability and depression in some
Hot flashes as skin blood vessels undergo intense vasodilation
Gradual thinning of the skin and bone loss
Increased total blood cholesterol levels and falling HDL